JP6488896B2 - Package sealing method and sealing paste - Google Patents

Description

  The present invention relates to a package sealing method and a sealing paste, and more particularly to a package sealing method and a sealing method using a mixed powder paste with high freedom of supply and easy composition control in an airtight / vacuum sealing material. It relates to a paste for stopping.

  Usually, as an airtight / vacuum sealing material, a solder having a melting point of less than 450 ° C. or a brazing material having a melting point of 450 ° C. or more is used. In addition, what is called a seal ring is used as a sealant to seal the lid and package, and the lid or package is sealed with Ni (nickel) plating, or the seal ring itself In some cases, a Ni plating is applied to the sealing portion. In addition, glass or resin may be used as a sealing material.

  For solder materials, lead-free solder materials such as Pb (lead) -63 mass% Sn (tin) and Sn-3 mass% Ag (silver) -0.5 mass% Cu (copper), Pb-10 mass% Sn and Au High temperature solder such as (gold) -20 mass% Sn is used. As the brazing material, Ag brazing is mainly used. Ag-22 mass% Cu is first and Ag-22 mass% Cu-17 mass% Zn (zinc) -5 mass% Sn, Cd (cadmium) and Ni. The one containing is used. Examples of the seal ring and the cover material include Kovar and 42 alloy, which are subjected to Ni plating.

  As a sealing method, when using a solder material, the solder plate is processed into a ring shape, sandwiched between the lid material and the package, melted and sealed using a furnace or oven, or covered with a solder paste or the like. A ring-shaped solder frame may be formed on the material and then sealed with the package. On the other hand, Ag brazing is performed by punching an Ag brazing plate into a ring shape, sandwiching it between the lid and the package, and using a seam welding machine, a laser welding machine, or the like to locally raise the sealing portion to a high temperature state. Ni plating formed on the seal ring is melted and sealed.

When sealing with a brazing method using Ag brazing or a Ni-plated seal ring, it is necessary to sandwich and seal between the lid material and the package, which is inefficient and inefficient.
Therefore, a method has been proposed in which Ag brazing powder is formed into a paste, printed on a lid, and heat-treated to form a sealing frame.

  In Patent Document 1, in a metal paste for sealing comprising a metal powder and an organic solvent, the metal powder has a purity of 99.9% by weight or more and an average particle size of 0.1 μm to 1.0 μm. The metal paste for sealing which mix | blended the metal powder which consists of gold powder, silver powder, platinum powder, or palladium powder in the ratio of 85 to 93 weight% and the organic solvent in 5 to 15 weight% is disclosed. As a sealing method using this metal paste, the metal paste is applied and dried, sintered at 80 to 300 ° C. to form a metal powder sintered body, and then the base powder is heated while heating the metal powder sintered body. A method for pressurizing the cap member is described.

  The metal paste described in Patent Document 1 uses a single metal powder of gold powder, silver powder, platinum powder, or palladium powder, and is not an alloy paste.

  On the other hand, Patent Document 2 discloses a silver brazing clad material comprising a base material made of a low thermal expansion metal and a low-temperature silver brazing material layer bonded to at least one surface of the base material. Yes. In this case, the silver brazing filler metal layer is coated with a paste made by mixing a medium composed of a solvent and a binder with metal powder made of a low-temperature type silver brazing filler, and then heated to melt the metal powder. It is formed by rapid solidification and further rolling. Specific examples of the silver brazing material include silver-copper-tin alloys, silver-copper-indium alloys, and silver-copper-zinc alloys. The silver brazing clad material is processed into a predetermined size by punching or the like to form a package sealing lid.

JP 2008-28364 A JP 2006-49595 A

  However, in the case of Ag brazing paste, it was necessary to heat-treat at a temperature higher than the melting point of Ag brazing at the time of forming the sealing frame, and then perform welding again at the time of sealing. In addition, since powder is formed with an Ag brazing alloy, when a different alloy composition is desired, the manufacturing of the alloy and the powder forming process again are very troublesome.

  An object of the present invention is to provide a package sealing method and a sealing paste capable of easily forming a sealing frame and easily changing the alloy composition.

  The package sealing method of the present invention is a package sealing method in which a lid is overlapped on a package and joined by a braze alloy, and a low melting point metal powder, a high melting point metal powder having a melting point higher than that of the low melting point metal powder, A paste applying step for applying a sealing paste containing a binder to the surface of the lid, and a brazing precursor obtained by melting the low-melting-point metal powder in the sealing paste applied to the lid And a pre-heat treatment step for forming the brazing body, and an alloying step for heating and melting the brazing precursor until it is joined to the package or joining the lid body to the package to form the brazing alloy.

  In this sealing method, after applying a sealing paste containing a low melting point metal powder and a high melting point metal powder to the lid, the low melting point metal powder is heated and melted by a pre-heat treatment step to obtain a surface of the lid. A nail precursor is formed. Since the paste is applied, the brazing precursor can be easily formed into a frame shape. Moreover, this preliminary heat treatment process melts the low melting point metal powder and can be performed at a low temperature. In this pre-heat treatment step, most of the refractory metal powder remains in a solid state, and the liquid phase of the low melting point metal penetrates between these solid refractory metal powders to cool and solidify each other. It is in a state attached to. This state is referred to as a wax precursor, and this wax precursor is fixed to the surface of the lid and does not fall off during handling.

  The brazing precursor can be alloyed by melting the refractory metal powder, and the alloying process may be performed until the lid is joined to the package or when they are joined.

  In the sealing method of the present invention, the alloying step may be performed in a state where the lid body after the preliminary heat treatment step is overlaid on the package. The brazing precursor can be alloyed and sealed simultaneously, which is efficient.

  Further, the melting point of the low melting point metal powder may be less than 300 ° C., and the melting point of the high melting point metal powder may be 300 ° C. or more.

  In the package sealing method of the present invention, it is preferable to have a binder removal step for removing the binder remaining in the brazing precursor between the preliminary heat treatment step and the alloying step, and the binder removal step. May include a cleaning process for cleaning the wax precursor with a cleaning liquid and a baking process for heat-treating the wax precursor after the cleaning process.

  In the package sealing method of the present invention, in the paste application step, the sealing paste is applied to the surface of a plate material having a size capable of forming a plurality of the lids, and after the preliminary heat treatment step, It is good to have the singulation process which divides | segments a board | plate material into the said cover body.

  The package sealing method of the present invention may have a plating treatment step of performing metal plating on the surface of the lid after the individualization step. Metal plating is applied as metallization of the lid, but if the metal plating is performed after dividing the lid, the metal plating is also applied to the side wall of the lid, which can effectively prevent side wall corrosion and rust. .

The sealing paste used in this sealing method, Ri greens contain a high melting point metal powder is higher melting point than the low melting point metal powder and the low melting point metal powder, the low melting point metal powder and the refractory metal powder, Ru metal der to form a Ag-Cu-Sn alloy or Ni-Sn alloy by being heated and melted.

  In this case, each metal powder may be a single metal powder of each metal component constituting the brazing alloy, or may be an alloy powder. When a single metal powder is used, it is preferable that a single metal powder having the lowest melting point in the alloy component constituting the brazing material is a low melting metal powder, and other metal single powder is a high melting metal powder. When the alloy powder is used, the alloy composition is adjusted so that the low melting point metal powder is melted at a lower temperature (for example, less than 300 ° C.) than the high melting point metal powder.

  In this case, Sn alone may be used as the low melting point metal powder, or Sn alloy powder added with some Ag and Cu may be used as the low melting point metal powder. Although the refractory metal powder is mainly composed of Ag and Cu, Ag and Cu may be mixed as a single powder or may be mixed as an alloy powder.

  In the sealing paste of the present invention, the low melting point metal powder may have a melting point of less than 300 ° C., and the high melting point metal powder may have a melting point of 300 ° C. or more.

  According to the present invention, the brazing precursor is fixed to the lid by the low melting point metal melted in the preliminary heat treatment step, so that a stable sealing frame can be easily formed on the lid, and the powders are appropriately combined. Thus, the alloy composition can be easily changed.

It is a perspective view of the principal part which shows the state which printed and apply | coated the sealing paste on the cover body by the method of this invention. It is a front view which shows the process of joining the cover body produced in FIG. 1 to a package.

  Embodiments of the present invention will be described below with reference to the drawings.

<Configuration of sealing paste>
First, an embodiment of a sealing paste used in the sealing method of the present invention will be described.

  This sealing paste contains a low-melting-point metal powder and a high-melting-point metal powder having a melting point higher than that of the low-melting-point metal powder. The metal powder is combined with a binder composed of an organic solvent, a resin, or the like. Kneaded.

  When an Ag—Cu—Sn based brazing alloy is used as the brazing alloy, each of the metal powders Ag powder, Cu powder, and Sn powder is mixed with the desired composition ratio (for example, 72 mass% Ag— 18% by mass Cu-10% by mass Sn). Among these, Sn has a lower melting point (liquidus temperature) than Ag and Cu, and Sn powder corresponds to the low melting point metal powder.

  The average particle size of these metal powders is preferably 0.1 μm to 30 μm. If it is less than 0.1 μm, it is difficult to mix uniformly when forming a paste, and in the case of a low melting point metal, the degree of powder oxidation is large, and diffusion to the high melting point metal is difficult to proceed during liquid phase sintering. On the other hand, when the average particle size exceeds 30 μm, many large pores are generated in the brazing precursor after liquid phase sintering, and the binder tends to remain. In particular, the low melting point metal powder that melts first preferably has a smaller particle size than the high melting point metal powder.

  In addition to the Ag—Cu—Sn based brazing alloy, depending on the desired brazing alloy composition, a single metal powder composed of each metal component constituting the composition is mixed at a composition ratio of the brazing alloy and paste. do it.

  Further, the low melting point metal of the alloy components constituting the brazing alloy, in the above case, Sn may be a single low melting point metal powder, but the low melting point metal is the main component so that the melting point is less than 300 ° C. It is also possible to make a metal powder made of an alloy partially containing other alloy components. The same applies to the refractory metal powder, and a metal powder made of an alloy of a plurality of metals may be used.

<Sealing method>
An embodiment of a method for sealing a lid to a package using the above-described sealing paste will be described.

  In this sealing method, the above-mentioned sealing paste is printed on the surface of a plate material having a size capable of forming a plurality of lids and applied, and the sealing paste applied to the lid A pre-heat treatment step for melting a low melting point metal powder to form a brazing precursor, a binder removal step for removing the binder, an individualization step for cutting the plate material and dividing it into a lid, and a lid for the box A joining step (alloying step) for joining the lid to the package by melting and solidifying the entire brazing precursor over the package. As needed, you may have the metal-plating process process which performs metal plating on the surface of a cover body after an individualization process. Hereinafter, it demonstrates in order of this process.

[Paste application process]
A plate member 2 having a size capable of forming a plurality of lids 1 in an aligned manner is prepared, and the sealing paste 3 described above is superimposed on the package 5 on the surface of the lid 1 on the surface of the plate member 2. Print and apply in a frame shape according to the position. Discharge supply by a dispenser or the like may be used. As the material of the lid 1, the aforementioned Kovar, 42 alloy or the like is used, and Ni plating (metal plating) is applied to both surfaces or one surface of the surface.

[Pre-heat treatment process]
Prior to joining the lid 1 to the package, a pre-heat treatment (low-temperature reflow treatment) is performed on the plate 2 (cover 1) coated with the sealing paste 3 alone to form a sealing frame. Specifically, the sealing paste 3 applied to the plate material 2 is heated to a temperature higher than or equal to the melting point of the low melting point metal powder contained in the sealing paste 3 and lower than the melting point of the high melting point metal powder. Melt the metal powder. This pre-heat treatment only needs to melt the low melting point metal powder, and can be performed by reflowing (heat treatment) in a furnace or oven in which a normal solder material is used.

  When the low melting point metal powder melts, a liquid phase of the low melting point metal spreads between the high melting point metal powders that do not melt at the temperature of the pre-heat treatment. A combined sealing frame is formed. At this time, the low melting point metal and the high melting point metal may be partly alloyed, but most of the high melting point metal remains as the original powder. The state in which the high melting point metal powder is bound by the low melting point metal is referred to as a wax precursor 4.

  In the case of the above-described Ag—Cu—Sn brazing alloy, the high melting point metal powder is obtained by melting the Sn powder as the low melting point metal powder into the liquid state with respect to the Ag powder and the Cu powder as the high melting point metal powder. It enters in between and liquid phase sintering proceeds. Thereby, the board | plate material 2 (lid body 1) with which the paste 3 for sealing was fixed as the brazing precursor 4 (refer FIG. 2) on low heat processing conditions is formed. However, at this time, it is not an Ag—Cu—Sn brazing alloy.

  Since the sealing frame of the brazing precursor 4 formed in this manner is fixed to the surface of the plate material 2 (lid body 1), it falls off from the lid body 1 when the plate material 2 (lid body 1) is handled. There is nothing.

[Binder removal step]
As described above, the binder is kneaded in the sealing paste 3, and therefore, the binder residue remaining in the preliminary heat treatment process is removed with a cleaning liquid. As the cleaning solution, Arakawa Chemical Industries, Ltd. Pine Alpha Series and the like can be used.

  Further, after removing the binder residue with the cleaning liquid, if necessary, the binder residue that has not been completely removed with the cleaning liquid may be removed by further heat treatment (baking process). The heat treatment (baking treatment) may be allowed to stand for a certain period of time at a temperature at which the brazing precursor 4 does not melt. For example, it may be left at 450 ° C. for 1 to 2 hours.

[Individualization process]
Next, the plate member 2 on which the sealing frame made of the wax precursor 4 is formed is cut into individual lids 1.

[Plating process]
As described above, Ni plating was formed on the surface of the plate material 2 as metallization. The entire surface may be Ni plated. Thereby, Ni plating is given also to the cut surface (side wall) of the cover body 1, and it can prevent that corrosion, rust, etc. progress to the side wall of the cover body 1 after sealing. The Ni plating may be electroless plating or electrolytic plating, and the film thickness may be several μm. In addition to Ni plating, other metal plating may be used.

[Jointing process (alloying process)]
The separated lid body 1 is overlapped on the package 5 and resistance welding is performed to melt the brazing precursor 4, and the solidified body is cooled and solidified to join the lid body 1 to the package 5. The package 5 is made of ceramics or the like, and a gold plating layer, for example, is formed as a conductive metal layer on the joint surface with the lid 1.

  Seam welding is performed as resistance welding. In this seam welding, as shown in FIG. 2, the lid body 1 is overlapped so that the brazing precursor 4 is brought into contact with the package 5, the roller electrode 11 is brought into contact with the lid body 1, and a predetermined pressure is applied. In this state, it moves along the peripheral edge of the lid 1 while passing an electric current. The brazing precursor 4 is locally melted by the Joule heat corresponding to the current value. By appropriately setting the current value, the brazing precursor 4 is instantaneously heated to a temperature equal to or higher than the melting point of the brazing precursor 4 and melted. Can be made.

  Due to the melting of the high melting point metal powder, the entire brazing precursor 4 including the low melting point metal is in a molten state, an alloy of each contained metal is formed, and sealing is completed. Since a predetermined amount of Ag, Cu, and Sn is mixed in the sealing paste 3, the lid body 1 and the package 5 can be joined as an Ag—Cu—Sn brazing alloy. That is, this joining process is also an alloying process of the brazing precursor 4.

  In the method of bonding and sealing the lid body 1 and the package 5 in this way, a sealing frame made of the wax precursor 4 is formed in advance on the lid body 1, so that it is sealed when the lid body 1 is handled. The stop frame does not fall off from the lid 1 and is easy to handle. The forming operation of the brazing precursor 4 can be performed by heat treatment at a low temperature, and the workability is good.

  When the lid 1 is joined to the package 5, the brazing precursor 4 can be sealed as a desired brazing alloy, which is efficient.

  In the above-described embodiment, the Ag—Cu—Sn based brazing alloy has been exemplified. However, even if other brazing alloy is used, it is easy to use a paste containing each metal component constituting the brazing alloy as a metal powder. The present invention can be applied. For example, as a high melting point metal powder having a melting point of 300 ° C. or higher, Ag powder (0 to 80% by mass), Cu powder (0 to 40% by mass), Ni powder (0 to 99% by mass), Zn powder (0 to 35%) Mass%), Cd powder (0 to 35 mass%), Mn (manganese) powder (0 to 35 mass%), and low melting point metal having a melting point of less than 300 ° C. (liquidus is less than 300 ° C.). Examples of the powder include Sn powder (0 to 35 mass%), In (indium) powder (0 to 35 mass%), Bi (bismuth) powder (0 to 35 mass%), and solder powder (0 to 35 mass%). The high melting point metal and the low melting point metal may be appropriately mixed within the numerical range in parentheses to obtain a brazing alloy.

  Note that the brazing precursor 4 was alloyed when the lid 1 was joined to the package 5 (the joining process also served as the alloying process), but the brazing precursor 4 was alloyed before the joining. (Alternatively, an alloying step may be provided before the joining step).

  In addition, when alloying the brazing precursor 4, it is possible to heat in a high temperature furnace in addition to the resistance welding method as in the embodiment. Therefore, it can be sealed with high dimensional accuracy without causing looseness.

  In addition, the sealing paste 3 was applied to the plate material 2 having a size capable of forming a plurality of lids 1 and pre-heat-treated, but the sealing paste 3 was applied to the individually divided lids 1. May be pre-heated.

  For Examples 1 to 3 and Comparative Examples 1 and 2, the number of samples used in the experiment was 100, and the package was a ceramic (made of alumina) having a size of 3.2 mm × 2.5 mm and a thickness of 0.5 mm. As a metallization, a 0.5 μm Au plating layer was formed on a 5 μm Ni plating layer. The lid used was made of Kovar having a size of 3.1 mm × 2.4 mm and a thickness of 0.1 mm, and a 0.1 μm Au plating layer was formed on the 5 μm Ni plating layer as metallization.

  For Example 4 and Comparative Example 3, as the metallization of the lid, only a 5 μm Ni plating layer was formed, and no Au plating layer was formed. Other than that was the same as Examples 1 to 3 and Comparative Examples 1 and 2. The number of samples in Example 4 and Comparative Example 3 was also 100 each.

  In any case, a sealing paste was prepared by mixing a powder having an average particle diameter and a mixed powder ratio shown in Table 1 and a binder. At this time, the binder ratio was adjusted so that the paste viscosity would be 250 Pa · s ± 30 Pa · s. SAC305 in Table 1 is an alloy of Sn-3 mass% Ag-0.5 mass% Cu.

  After this sealing paste was applied to the lid, a pre-heat treatment at a maximum temperature of 240 ° C. was performed and washed to remove the binder to form a sealing frame. Thereafter, the state of the sealing frame was observed using a stereomicroscope. There was no problem in that the sealing frame was accurately formed even after cleaning, and the sealing frame in which the sealing frame was observed to be missing or chipped was regarded as defective. When this was regarded as a defect rate, the defect rate was less than 2%, and when it was 2% or more, the sample was rejected.

  Next, the lid was overlapped on the package and seam welded to perform hermetic sealing. Thereafter, a high pressure was applied to the inside in an airtight test, and a leaked product was determined to be defective, and the sealing performance was evaluated based on the defective rate. If the defective rate was less than 2%, it was accepted, and those with 2% or more were rejected.

  These results are shown in Table 1.

  As is apparent from Table 1, Examples 1 and 4 having a single metal powder Sn powder (melting point 232 ° C.) as a low melting metal powder, and a single metal powder In powder (melting point 156 ° C.) as a low melting metal powder. As for Example 2 which has as an example, and Example 3 which has alloy powder (SAC305: melting point 220 degreeC) which has Sn as a main component as a low melting metal powder, all have the favorable state of a sealing frame, and the sealing property to a package Thus, it can be seen that by sealing using the paste of the present invention, the sealing frame is stably fixed to the lid and the sealing performance to the package is high.

DESCRIPTION OF SYMBOLS 1 Cover body 2 Board | plate material 3 Sealing paste 4 Wax precursor 5 Package 11 Roller electrode

Claims (9)

  A package sealing method in which a lid is placed on a package and joined by a braze alloy, the sealing method comprising a low melting point metal powder, a high melting point metal powder having a higher melting point than the low melting point metal powder, and a binder A paste applying step of applying a paste for the surface of the lid, a pre-heat treatment step of melting the low melting point metal powder in the sealing paste applied to the lid to form a brazing precursor, A package sealing method comprising: an alloying step in which the brazing precursor is heated and melted and alloyed until the lid is joined to the package or when the lid is joined.   2. The package sealing method according to claim 1, wherein the alloying step is performed in a state where the lid after the pre-heat treatment step is overlaid on the package.   3. The package sealing method according to claim 1, wherein the low melting point metal powder has a melting point of less than 300 ° C., and the high melting point metal powder has a melting point of 300 ° C. or more.   The binder removing step of removing the binder remaining in the brazing precursor is provided between the preliminary heat treatment step and the alloying step. Package sealing method.   5. The package sealing method according to claim 4, wherein the binder removing step includes a cleaning process for cleaning the wax precursor with a cleaning liquid, and a baking process for heat-treating the wax precursor after the cleaning process. .   In the paste application step, the sealing paste is applied to the surface of a plate material having a size capable of forming a plurality of the lids, and the plate material is divided into the lids after the preliminary heat treatment step. The package sealing method according to claim 1, further comprising a singulation step.   The package sealing method according to claim 6, further comprising a plating treatment step of performing metal plating on a surface of the lid after the singulation step. Ri Na contain a refractory metal powder higher melting point than the low melting point metal powder and the low melting point metal powder, the low melting point metal powder and the refractory metal powder, Ag-Cu-Sn by being heated and melted sealing paste, wherein the metal der Rukoto to form an alloy or Ni-Sn alloy. 9. The sealing paste according to claim 8, wherein the low melting point metal powder has a melting point of less than 300 ° C., and the high melting point metal powder has a melting point of 300 ° C. or more.

Images